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The role of motor cortex in speech perception

Donnerstag, 31. Mai 2018, 16:15 Uhr bis 18:00 Uhr

Human motor circuits are active during speech perception. However, the precise conditions under which the motor system is active during speech perception are not clear. Two current accounts make distinct predictions for how listening to speech engages speech motor representations. The first account suggests that the motor system is most strongly activated when observing familiar actions while a second account asserts that motor excitability is greatest when observing less familiar, ambiguous actions. I will first discuss how we investigated these predictions using transcranial magnetic stimulation (TMS) by measuring Motor Evoked Potentials (MEPs) in lip and hand motor cortex. Second, I will discuss an experiment in which we aimed to further clarify the precise nature of activation of articulatory motor representations during speech perception. Firstly, it is unknown whether speech motor activity is preferentially engaged when perceiving forms of motor-based signal distortion (form dependent), or if motor activity is facilitated whenever perception is challenged, irrespective of the source of the difficulty (form independent). Third, it is unknown whether and how speech motor facilitation during speech perception is moderated by hearing ability, despite hearing sensitivity being paramount to understanding speech in challenging conditions. We investigated these questions in a final MEP experiment including younger and older listeners.